Problem: $\dfrac{9}{5} - \dfrac{7}{10} = {?}$
$ = {\dfrac{9 \times 2}{5 \times 2}} - {\dfrac{7 \times 1}{10 \times 1}} $ $ = {\dfrac{18}{10}} - {\dfrac{7}{10}} $ $ = \dfrac{{18} - {7}}{10} $ $ = \dfrac{11}{10}$